A room, space, corner or area of a dwelling that is specifically reserved for a female person to be in a solitary condition, away from the rest of the household, in order to relax, get dressed, perform personal hygiene maneuvers, or entertain friends without interruption.

The dream Clam Shack includes a walk-in closet/dressing room/bathroom combination and mini-bar stocked with wine, bitch pop, etc. The average Clam Shack is more likely a closet or bathroom with a bottle of vodka stealthily stowed in an old ski boot or under the sink.

LAUREL: "Hey Carol, Katie and Bev are coming over after work to chill in the clam shack with some Pinot if you want to join."
CAROL: "Sounds good. I'll need a whole bottle to myself after the day I've had"
LAUREL: "No probs, I have a case"